The field of network security has become increasingly important in today's society. The Internet has enabled interconnection of different computer networks all over the world. In particular, the Internet provides a medium for exchanging electronic mail (email) between different users connected to different computer networks via various types of client devices. While the use of email has transformed business and personal communications, it has also been used as a vehicle for malicious operators to gain unauthorized access to computers and computer networks and for intentional or inadvertent disclosure of sensitive information.
Malicious software (“malware”) that infects a host computer may be able to perform any number of malicious actions, such as sending out spam or malicious emails from the host computer, stealing sensitive information from a business or individual associated with the host computer, propagating to other host computers, and/or assisting with distributed denial of service attacks, for example. Organizations often protect their computer networks from inbound email threats using some type of email protection device to filter out potentially harmful emails. Cloud services can provide inbound email filtering (e.g., spam, malware), which can help conserve bandwidth for a network. Other mechanisms, however, are generally employed to monitor outbound email, however, to prevent the loss of sensitive or confidential information. Hence, significant administrative challenges remain for protecting computers and computer networks from malicious and inadvertent exploitation via inbound and outbound emails.